Deionized-water cooling system for electrical equipment

ABSTRACT

Deionized-water cooling system for electrical equipment, connected electrically to a primary power supply, characterized in that it includes: a main circuit to channel and cool the deionized water intended to circulate within the electrical equipment; a main pumping system; a main power source; a deionization circuit connected at two points to the main circuit and including a deionizer; a secondary pumping system to circulate the deionized water in the deionizer, and a secondary power source, which secondary power source has less power than the main power source. 
     Application to the cooling of an underwater power converter.

This invention concerns a deionized-water cooling system for electricalequipment.

The invention applies in particular to underwater electronic andelectrotechnical equipment protected in water-proof housings for depthsof 0 to approximately 6,000 meters in particular distribution ortransmission systems, as well as power converters typically of 100 kVAto several hundred MVA.

Such equipment must generally be cooled. A known-art cooling methodconsists in having deionized, cooled water circulate in the equipment inquestion. The circulation of the water is ensured using pumps requiringa significant amount of electrical power, on the order of 5-30 kVA.

These pumps are supplied with electrical power by a power supplyexternal to the equipment in question. In order to maintain anappropriate deionization level in the cooling water circuit, the pumpsmust be supplied during the normal operation of the equipment to becooled, i.e., whilst the latter is running and had by the power grid,but also when the equipment is stopped and not powered up. In fact, itis generally not permitted to run electrical power through the equipmentunless the deionization level of the cooling water is sufficient.

One objective of the invention is to provide a deionized-water coolinghaving an auxiliary power supply with a relatively insignificant powerconsumption while the equipment to be cooled is stopped.

To this end, the invention seeks to provide a deionized-water coolingsystem for electrical equipment, which equipment is electricallyconnected to a primary power source, characterized in that it includes:

-   -   a main circuit to channel and cool the deionized water to be        circulated within the electrical equipment;    -   a main pumping system to circulate the deionized water within        the main circuit; a main power source to supply the main pumping        system;    -   a deionization circuit connected to two points of the main        circuit to deionize the water of the main circuit, which        deionization circuit includes a deionizer;    -   a secondary pumping system to circulate the deionized water        within the deionizer; and    -   a secondary power source to supply the secondary pumping system;        which secondary power source has less power than the main power        source.

According to specific embodiments, the cooling system may include one ormore of the following characteristics, individually or in alltechnically possible combinations;

-   -   the ionization circuit is hydraulically mounted on the terminals        of the main pumping system, and the secondary pumping system is        hydraulically mounted on the terminals of a portion of the        deionization circuit including the deionizer;    -   it additionally includes elements to cause hydraulic pressure        losses, which elements are actuated such that, when the main        pumping system is stopped and the secondary pumping system is        operating, the secondary pumping system circulates a first flow        of deionized water in the main circuit and a second flow of        deionized water in the deionizer;    -   the elements to create the hydraulic pressure losses include one        or more check valves located within the main pumping system and        a throttle located within the deionization circuit outside of        the portion of the deionization circuit on the terminals of        which the secondary pumping system is mounted.

The invention also concerns an electrical system characterized in thatit includes:

-   -   electrical equipment intended to be supplied with electrical        power by a primary power supply; and    -   a deionized-water cooling system as described above, to cool the        electrical equipment.

According to specific embodiments, the electrical system may include oneor more of the following characteristics, individually or in alltechnically possible combinations:

-   -   the main power source is connected to the main power supply of        the electrical equipment;    -   it additionally includes a water-proof housing, which housing        protects the electrical equipment, the main pumping system, the        deionizing circuit, and the secondary pumping system;    -   the secondary power source is located outside of the housing;    -   it is underwater;    -   the electrical equipment is an electronic power converter.

The invention lastly concerns a method of cooling of an electricalsystem as described above, characterized in that it includes thefollowing steps:

-   -   when the electrical equipment is operating, power is supplied to        the main pumping system of the cooling system by the main power        source so as to circulate the deionized water in the main        circuit and the deionization circuit of the cooling system, and    -   when the electrical equipment is stopped, power is supplied to        the secondary pumping system of the cooling system by the        secondary power source in order to circulate deionized water in        at least one portion of the deionization circuit including the        deionizer and in the main circuit.    -   According to a specific embodiment, the electrical system may        include the following characteristic:    -   in the step in which the main pumping system is supplied with        power, the secondary pumping system is stopped, and in the step        in which the secondary pumping system is supplied with power,        the main pumping system is stopped.

These invention will be more easily understood based on the followingdescription, provided by way of example only, and by reference to thedrawings appended hereto, on which:

FIG. 1 is a partial schematic of a system disclosed by the invention,focusing on the hydraulic aspects,

FIG. 2 is a partial schematic of a system disclosed by the invention,focusing on the electrical aspects.

The electrical system shown in FIGS. 1 and 2 is intended to besubmerged, in particular in the sea. It includes a housing, electricalequipment, a main circuit for the cooling of the electrical equipment, adeionization circuit to deionize the water of the main circuit, a mainpumping system, and a secondary pumping system.

The housing is designed to be water-proof in conditions arising due tothe immersion of the electrical system.

The electrical equipment is a power converter, having power ranging from50 kVA to several hundred MVA. The electrical equipment is electricallyconnected to an underwater electrical cable (shown in FIG. 2), forming aprimary power supply, and converts the power supplied by this supply.

The main circuit includes a heat exchanger and deionized water conduits.The exchanger is located outside the housing to carry out heat exchangebetween the deionized water and external water so as to cool thedeionized water. The output of the exchanger is connected hydraulicallyto the main pumping system via the conduit. The output of the mainpumping system is hydraulically connected by the conduit to an input ofthe electrical equipment. The deionized water that has circulated withinthe electrical equipment is recovered in the conduit, returning it tothe exchanger The main pumping system is intended to move the deionizedwater in the main circuit and in the deionization circuit, The maincircuit and the main pumping system form a loop.

The main pumping system includes a first pumping assembly, consisting ofa pump and a check valve located on the discharge of the pump. The mainpumping system also includes a second pumping system mounted parallel tothe first pumping assembly, and also consists of a pump and a checkvalve located at the discharge of the pump. The second pumping assemblyis redundant, improving the reliability of the main pumping system.

The deionization circuit is presented as an open circuit, mountedhydraulically parallel to the terminals A and B of the main pumpinggroup. Thus, the main pumping system may move the deionized water in themain circuit and the deionization circuit ; the flows within these twocircuits may be different.

The deionization circuit includes a deionizer and a flow-controllingelement following the deionizer. In this example, the deionizer includesa bottle containing a resin, and the flow-controlling element is a gatecontrolled by a resistance indicator of the deionized water. The role ofthe deionization circuit is to maintain a certain deionization rate,verifiable, for example, by a measure of the resistance of the deionizedwater in the main circuit. If the measured resistance decreases, theflow-controlling element permits a greater flow in the deionizationcircuit in order to increase deionization.

The secondary pumping system includes a pump and a check valve locateddownstream from the pump. The secondary pumping system is presented asan open circuit, hydraulically mounted on the terminals A′ and B′ of aportion of the deionization circuit, including the deionizer and theflow-controlling element. A throttle is included in the deionizationcircuit, between points A and A′, in another portion of the deionizationthan that to the terminals of which the secondary pumping system ismounted. Thus, the secondary pumping system can ensure a water flowwithin the deionizer and a flow within the main circuit. The throttleallows for regulation of the flow within the main circuit. The greaterthe throttle, the greater the flow in the deionizer.

On the electrical schematic shown in FIG. 2, the pumps of the mainpumping system are connected electrically to a main power source, which,in turn, is connected to the power cable of the electrical equipment.The role of this main power source is to process the power supplied,from 5 to 30 kVA, to a switch and control board of the pumps. When theelectrical equipment is supplied with power, the main pumping system maytherefore be supplied with power without using an auxiliary source.

The secondary pumping system is electrically connected to a secondarypower source, on the order of 1 kVA, via an electrical switch board.Thus, the secondary pumping system may supply power even when theelectrical equipment is not powered up. The secondary power source isoutside of the water-proof housing. It is relatively small in volume,and, when it is used to supply the secondary pumping system, does notentail significant power consumption. Additionally, the secondary powersource may be more easily backed up, due to its size, than the mainpower source.

The operation of the system is described below. When the electricalequipment is operating (normal mode), only one of the pumping assembliesof the main pumping system is actuated. This ensures a flow on the orderof 10-200 m³/h in the main circuit and 25-500 l/h in the deionizationcircuit. The power supply for the pumps thus originates solely from themain power source, which power is taken from the cable supplying theelectrical equipment.

When the electrical equipment is stopped (“stop” mode), only thesecondary pumping system is operating. This ensures a reduced flowwithin the main circuit, on the order of 100 l/h-2 m³/h, and a flowthrough the deionizer sufficient to allow for deionization. The flowthat can be obtained in the deionizer is greater than or equal to thatexisting within the deionizer during normal operating mod (25-500 l/h).The throttle allows for control of the flow via the deionizer.

Thus, in “stop” mode, the power required by the pumping system may besupplied by a power source of approximately 1 kVA, This power is lowerby approximately one order of magnitude than that required when the mainpumping system must be actuated (5-30 kVA). The secondary power sourceused is thus reduced in size. The power consumed by the pumping systemin “stop” mode is also reduced to an analogous degree.

In other words, the invention reaches its objective due to the factthat, while the electrical equipment to be cooled is operating andsignificant electrical power is required to actuate the pumps of themain pumping system, these are supplied with electrical power by a mainpower source connected to the power cable of the electrical equipment tobe cooled. When, on the other hand, the latter is not in operation, asecondary pumping system is used to move the water in the deionizer andthe main circuit. The water flow is moderate then, because its principalobjective is to maintain an appropriate deionization level. This flowalso allows for heat exchange between the electrical equipment and theexternal environment. This is useful, e.g., following a cold shutdown ofthe electrical equipment, when the secondary power source may have beenbacked up. in order to ensure the evacuation of the residual heat fromthe electrical equipment.

Accordingly, the secondary pumping system may be supplied by a secondarypower source smaller than that required for the main pumping system, onthe order of 1 kVA. This corresponds to a reduction of approximately oneorder of magnitude. The power consumed by the cooling system in “stop”mode is also reduced to an analogous degree.

According to another embodiment, not shown, the deionization circuit mayfollow the main pumping system. The parallel connection showed by FIG.1, however, has the advantage of the flow within the deionizer beingable to be different to the flow within the main circuit.

According to another embodiment, the throttle may be placed, in thedeionization circuit, on the side opposite the deionizer, between pointsB and B. It may also be placed in the main circuit, but this has thedisadvantage of creating a pressure loss that must be overcome by themain pumping system, resulting in a loss of power in “normal” operation.

According to another embodiment (not shown), the main power sourceconnected to the power cable is backed up. This allows for continued useof the main power source to supply the main pumping system, even whenthe electrical equipment is not supplied by the cable.

According to an alternative embodiment (not shown), the main powersource is an autonomous power source, not connected to the cable. Thisallows for continued use of the main power source to supply the mainpumping system, even when the electrical equipment has no power supply.

The continued use of the main pumping system, when the electricalequipment is stopped, creates a need to cool the electrical equipment,e.g., following a cold shutdown, when a significant amount of heat mustbe evacuated.

1. Deionized-water cooling system for electrical equipment, whichelectrical equipment is connected electrically to a primary powersupply, characterized in that it includes: a main circuit to channel andcool the deionized water to be circulated within the electricalequipment; a main pumping system to circulate the deionized water withinthe main circuit; a main power source to supply the main pumping system;a deionization circuit connected to two points of the main circuit todeionize the water of the main circuit, which deionization circuitincludes a deionizer; a secondary pumping system to circulate thedeionized water within the deionizer; and a secondary power source tosupply the secondary pumping system; which secondary power source hasless power than the main power source.
 2. A deionized-water coolingsystem according to claim 1, characterized in that: the deionizationcircuit is hydraulically mounted on the terminals of the main pumpingsystem; and the secondary pumping system is hydraulically mounted to theterminals of a portion of the deionization circuit including thedeionizer.
 3. A deionized-water cooling system according to claim 1 or2, characterized in that it additionally includes elements to causehydraulic pressure losses, which elements are actuated such that, whenthe main pumping system is stopped and the secondary pumping system isoperating, the secondary pumping system circulates a first flow ofdeionized water in the main circuit and a second flow of deionized waterin the deionizer;
 4. A deionized-water cooling system according to claim3, characterized in that the elements to create hydraulic pressurelosses include one or more check valves located within the main pumpingsystem and a throttle located within the deionization circuit outsidethe portion of the deionization circuit on the terminals of which thesecondary pumping system is mounted.
 5. Electrical system characterizedin that it includes: electrical equipment intended to be supplied withelectrical power by a primary power supply: and a deionized-watercooling system according to any of the foregoing claims to cool theelectrical equipment.
 6. Electrical system according to claim 5,characterized in that the main power source is connected to the primarypower supply of the electrical equipment.
 7. Electrical system accordingto claim 5 or 6, characterized in that it additionally includes awater-proof housing, which housing protects the electrical equipment,the main pumping system, the deionization circuit, and the secondarypumping system.
 8. Electrical system according to any of claims 5-7,characterized in that the secondary power source is located outside ofthe housing.
 9. Electrical system according to any of claims 5-8,characterized in that is underwater.
 10. Electrical system according toone of claims 5-9, characterized in that the electrical equipment is anelectronic power converter.
 11. Method for cooling an electrical systemaccording to any of claims 5-10, characterized in that it includes thefollowing steps: when the electrical equipment is operating, power issupplied to the main pumping system of the cooling system by the mainpower source so as to circulate the deionized water in the main circuitand the deionization circuit of the cooling system, and when theelectrical equipment is stopped, power is supplied to the secondarypumping system of the cooling system by the secondary power source inorder to circulate deionized water in at least one portion of thedeionization circuit including the deionizer and in the main circuit.12. Method of cooling an electrical system according to claim 11,characterized in that: in the step in which the main pumping system issupplied with power, the secondary pumping system is stopped, and in thestep in which the secondary pumping system is supplied with power, themain pumping system is stopped.